1. Field of the Invention
The invention relates to a bit position encoder, intended for use in equipment such as facsimile equipment, for searching a bit string for a bit having a predetermined value.
2. Description of the Related Art
A bit position encoder is a device which searches a bit string of 8 bits from right to left or from left to right for, for example, high bits (1s) and encodes the first high-bit position into 3-bit data. In a conventional bit position encoder, the output of a search circuit which has searched for a high bit first is transferred to the adjacent search circuit. Thus, the output of the adjacent search section is not determined during the data propagation. The operating speed of the bit search circuit depends therefore on the time required to propagate data.
In the case of a bit position encoder for an 8-bit string, it is when input data D7 to D0=00000001 is searched from LSB (right) to MSB (left) that it takes a maximum amount of time for output data to be determined. In order to transfer data of a 1, a delay time corresponding to 16 gates will be required. The delay time becomes longer as data to be searched increases in bit length to 16 bits, 32 bits. Therefore, a problem arises in that difficulties are involved in speeding up the bit search.